The purpose of this study is to develop a dietary protocol and maintain metabolic conditions which are conducive to the development, in various animal species, of experimental atherosclerosis similar to human disease. This has been achieved in dogs, miniature swine, and Patas monkeys. for these species the source of dietary fat has been found to profoundly affect the type, distribution, and severity of the disease. Atherosclerosis produced by diets containing beef tallow is severe and is associated with gross arterial thrombosis and occlusive vascular disease.